1. Field of the Invention
The present invention relates to electrical connector housings used for example in automobiles. More particularly, the electrical connector housing according to the present invention is used as a junction box that contains a plurality of branch circuits and on which electrical relays, fuses and electrical connectors can be mounted. In the electrical connector housing of the present invention, the circuit configuration can be standardized for making it easier to form circuitry and to respond to changes of the circuitry.
2. Description of Background Information
The automobile industry is continually searching for the most efficient way of reducing the costs of manufacturing wire harnesses used in automobiles. In this connection, it is very important to optimize the structural and wiring design of an electrical connector housing. This applies both to internal circuits and connector receptacles for receiving external terminals and as well as to a corresponding connector assembly including external terminals that fit into the connector receptacles.
Automobiles are filled with different kinds of electrical parts or electrical apparatuses, depending on their grades, types or models. Usually, the higher the grade of automobile is, the greater the number of circuits are used. In order to respond to the variations in this number of circuits as a function of the vehicle depending on grades, it is preferable to standardize structures of electrical connector housings, bus bars contained in the electrical connector housings, and connector assemblies received by connector receptacles of the electrical connector housings. These standardized elements can be used for all automobile grades and thus gain a wider use.
By contrast, the number of external terminals contained in a connector assembly is determined by the automobile's grade. Thus, a connector assembly contains only the number of external terminals necessary for a particular grade. For instance, for two different car grades of an identical model, the electrical connector housing, its bus bars and the connector assembly may be structurally standardized. The only difference is that some circuits for a connector assembly of high comfort apparatuses are not provided for the connector assembly of low grade cars. In this context, the low-grade connector assembly is not provided with the outer terminals sufficient to connect with all the available bus bars contained in the electrical connector housing.
FIG. 1 shows an electrical connector housing conventionally used in automobiles. Such an electrical connector housing is a case consisting of a lower case 1 and an upper case 2. The case contains bus bars 3 and insulating plates 4 stacked in alternation. The bus bar 3 is made by stamping out a given form of circuitry from an electrically conductive plate, and includes a series of projecting tabs 3a. Relays, fuses or connectors are mounted in fitting units formed on the lower case 1 and/or the upper case 2. The tabs 3a are connected to electrical relays, fuses or connectors via transit terminals (not shown in the figures).
In some cases, coated conductive wires are used instead of bus bars 3 Press-fit contact members are then press-fitted to the coated conductive wires, and the coated conductive wires are connected to relays, fuses or connectors via transit terminals.
When bus bars are used, their design must be changed each time the routings need to be modified. The circuitry modification calls for change of molds used for bus bar manufacturing and thus incurs high costs. It is also difficult to respond quickly to circuit modifications or additions. Alternatively, when coated conductive cables or wires and press-fit contact members are used, the coated conductive cables have to be wired along a given routing. To this end, guiding members have to be provided on insulating plates or on the inner surface of the case. Accordingly, when circuitry is modified or added, the insulating plates and the case, as well as the molds for making them, have to be changed. The consequent need to make a new mold also incurs high costs, just as in the case of bus bars.
To solve these problems, standardized circuit elements have been developed, in which modifications or additions can easily be made (FIGS. 2(A)-2(D) and 3).
FIGS. 2(A)-2(D) show branch connection boxes designed by the present inventors and published as Japanese Utility Model HEI-5-55718. The branch connection boxes have two cases 6, 6 of an identical configuration, each including the same number of connector receptacles 5a in a surface and a rear surface opposite to the surface where the connector receptacles are provided. Cases 6 contain a plurality of bus bars 7 each one having an identical bifurcate fork-shape symmetrical about its longitudinal center axis. The two cases 6, 6 are then engaged back to back, i.e., the rear surfaces face each other so that the connector receptacles 5a face in opposite directions. The bus bars 7 are then mounted into the cases 6, 6 such as to be aligned parallel to one another. Subsequently, electrical cables 8 are pressed into the center portion of bifurcate fork shape bus bars 7, so that the bus bars 7 and the electrical cables 8 are electrically connected.
FIG. 3 shows an electrical connection box disclosed in U.S. Pat. No. 5,057,026. In this box, bus bars 9 have a fixed narrow width, and are arranged in parallel. The bus bars 9 are provided, at given positions, with tabs 9a including contact blades. Electrical cables 10 are aligned in a direction perpendicular to the bus bars 9 and connected thereto by pushing down into the contact blades. Bus bars 9 and electrical cables 10 thus form a planar circuit stackable on an insulating plate 11, and a plurality of such units are formed into a layered structure. A connector assembly 12 is arranged nearby alongside the layered structure. The layers of bus bars 9 are then connected to one another through the connector assembly 12.
In the branch connection boxes shown in FIGS. 2(A)-2(D), a connector assembly is fitted into a corresponding connector receptacle 5a. When the connector assembly is not provided with a sufficient number of outside terminals, as is the case of low-grade connector assemblies, a considerable number of bus bars 7 may be left unconnected to any outside terminal and thus not used as circuits. Further, the space for containing connectors is limited, so that, when the number of circuits is increased, the width of the case must be broadened. It then becomes more difficult to produce higher density circuitry.
In the electrical connection box shown in FIG. 3, the lengths of bus bars 9 are determined beforehand, and the bus bars are aligned in parallel at given positions. The bus bars 9 are then connected to electrical cables by cramping to form circuits. This process requires several process steps and many connection sites, thus making their production complex. Besides, as a connector assembly 12 is needed for connecting the layers of bus bars 9, specific parts have to be prepared. Such complicated process steps and the provision of specific parts incur a high production cost.